FIG. 1 is a schematic diagram showing a structure of a conventional video camera. The video camera is composed of a lens module 101 and a camera main body 111. The lens module 101 is composed of an image forming lens 102 and an iris adjusting mechanism 103. The image forming lens 102 includes a focus lens 104. The camera main body 111 is composed of an optical LPF (low pass filter) 112, an image sensor 113, and a camera processing circuit 114.
Light of an object is entered into the image forming lens 102 and emitted to the image sensor 113 through the iris adjusting mechanism 103 and the optical LPF 112. Thus, an image of the object is formed on a light receiving plane of the image sensor 113. The image sensor 113 is composed of for example a charge coupled device (hereinafter abbreviated as CCD). The image sensor 113 photoelectrically converts the image of the object received on the light receiving plane into an electric signal. The resultant electric signal corresponding to the image of the object is supplied to the camera processing circuit 114. The camera processing circuit 114 performs a predetermined signal process for the image signal received from the image sensor 113. Thereafter, the image signal is recorded on a record medium such as a video tape. Alternatively, the image signal may be output to for example a monitor and displayed thereon. In addition, the image signal may be supplied to a computer so as to perform a predetermined process for the image signal.
The image sensor 113 receives a drive signal from the camera processing circuit 114. The image sensor 113 performs a predetermined process such as an image signal output process corresponding to the drive signal. The iris adjusting mechanism 103 adjusts the brightness of the image formed on the image sensor 113. In addition, the iris adjusting mechanism 103 shields unnecessary peripheral rays that are emitted from the image forming lens 102. The focus lens 104 adjusts the focus of the image formed on the image sensor 113. The optical LPF 112 is an optical device whose refractive index varies depending on the plane of polarization of the entered light. The optical LPF 112 is composed of for example a rock crystal with optical anisotropy. The optical LPF 112 limits high spatial frequency components of light emitted from the focus lens 104 so as to decrease loop-back distortion that takes place in the image sensor 113.
When a video camera is used as an image capturing device for a computer, a car monitoring device, a TV telephone, a TV conference system, and so forth, high image quality is not strictly required. In other words, in these applications, easy mounting and handling of the video camera are more important than high image quality.
However, to easily mount and handle the video camera, it should be optically adjusted in the fabrication stage. Thus, in addition to complicated fabrication steps of the video camera, the size and cost thereof increase.
In addition, the conventional video camera limits the optical spatial frequencies of light entered into the image sensor 113. Thus, as shown in FIG. 1, the optical LPF 112 is required. The thickness d of the optical LPF 112 should be proportional to the pitches of pixels of the image sensor 113. Consequently, when the pitches of pixels of the image sensor 113 are small, the cost thereof increases. When the pitches of pixels of the image sensor 113 are large, the thickness d of the optical LPF 112 becomes large.
As a small, low-cost video camera, a structure as shown in FIG. 2 is known. In this example, a CCD image pickup device 403 is secured on a substrate 404. In addition, one image forming lens 401 is secured to a lens barrel 402. The lens barrel 402 is secured to the substrate 404. Various parts 405 are mounted on the rear surface of the substrate 404.
In FIG. 2, the structure of a light amount adjusting mechanism and so forth is omitted.
The CCD image pickup device 403 is structured as shown in FIG. 3. In other words, the CCD image pickup device 403 has a CCD bare chip 403A that converts the entered light into an electric signal. The CCD bare chip 403A has color filters (not shown) that pass rays with predetermined wavelengths of R, G, and B (or complementary colors thereof). The CCD bare chip 403A is housed in a package 403B composed of plastics or the like. A cover glass 403C is disposed at the top of the package 403B.
However, in the structure shown in FIG. 2, the distance from the upper edge of the image forming lens 401 to the upper surface of the CCD image pickup device 403 is around 30 mm. The thickness of the CCD image pickup device 403 is 5 mm. The distance from the upper surface of the substrate 404 to the lower edge of the part 405 is around 15 mm. Thus, the total thickness becomes around 50 mm.
Thus, the structure as shown in FIG. 2 cannot be mounted to for example a PC card for use with a portable personal computer or the like.